Method and apparatus for substrate polishing

ABSTRACT

A method and apparatus are provided for polishing a substrate surface. In one aspect, an apparatus for polishing a substrate includes a conductive polishing pad and an electrode having a membrane disposed therebetween. The membrane is orientated relative the conductive pad in a manner that facilitates removal of entrained gas from electrolyte flowing towards the conductive pad. The apparatus may be part of an electro-chemical polishing station that may optionally be part of a system that includes chemical mechanical polishing stations.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate to a method and apparatusfor planarizing a substrate surface.

2. Background of the Related Art

In the fabrication of integrated circuits and other electronic devices,multiple layers of conducting, semiconducting, and dielectric materialsare deposited on or removed from a surface of a substrate. Thin layersof conducting, semiconducting, and dielectric materials may be depositedby a number of deposition techniques. Common deposition techniques inmodern processing include physical vapor deposition (PVD), also known assputtering, chemical vapor deposition (CVD), plasma-enhanced chemicalvapor deposition (PECVD), and electrochemical plating (ECP).

As layers of materials are sequentially deposited and removed, theuppermost surface of the substrate may become non-planar across itssurface and require planarization. Planarizing a surface, or “polishing”a surface, is a process where material is removed from the surface ofthe substrate to form a generally even, planar surface. Planarization isuseful in removing undesired surface topography and surface defects,such as agglomerated materials, crystal lattice damage, scratches, andcontaminated layers or materials. Planarization is also useful informing features on a substrate by removing excess deposited materialused to fill the features and to provide an even surface for subsequentlevels of metallization and processing.

Chemical mechanical planarization, or chemical mechanical polishing(CMP), is a common technique used to planarize substrates. CMP utilizesa chemical composition, typically a slurry or other fluid medium, forselective removal of material from substrates. In conventional CMPtechniques, a substrate carrier or polishing head is mounted on acarrier assembly and positioned in contact with a polishing pad in a CMPapparatus. The carrier assembly provides a controllable pressure to thesubstrate urging the substrate against the polishing pad. The pad ismoved relative to the substrate by an external driving force. The CMPapparatus effects polishing or rubbing movement between the surface ofthe substrate and the polishing pad while dispersing a polishingcomposition to effect chemical activity and/or mechanical activity andconsequential removal of material from the surface of the substrate.

One material increasingly utilized in integrated circuit fabrication iscopper due to its desirable electrical properties. However, copper hasits own special fabrication problems. For example, copper is difficultto pattern and etch, and new processes and techniques, such as damasceneor dual damascene processes, are being used to form copper substratefeatures. In damascene processes, a feature is defined in a dielectricmaterial and subsequently filled with copper. Dielectric materials withlow dielectric constants, i.e., less than about 3, are being used in themanufacture of copper damascenes. Barrier layer materials are depositedconformally on the surfaces of the features formed in the dielectriclayer prior to deposition of copper material. Copper material is thendeposited over the barrier layer and the surrounding field. However,copper fill of the features usually results in excess copper material,or overburden, on the substrate surface that must be removed to form acopper filled feature in the dielectric material and prepare thesubstrate surface for subsequent processing.

One challenge that is presented in polishing copper materials is thatthe conductive material and the barrier materials are often removed fromthe substrate surface at different rates, both of which can result inexcess conductive material being retained as residues on the substratesurface. Additionally, the substrate surface may have different surfacetopography, depending on the density or size of features formed therein.Copper material is removed at different removal rates along thedifferent surface topography of the substrate surface, which makeseffective removal of copper material from the substrate surface andfinal planarity of the substrate surface difficult to achieve.

One solution for polishing copper in low dielectric materials withreduced or minimal defects formed thereon is by polishing copper byelectrochemical mechanical polishing (ECMP) techniques. ECMP techniquesremove conductive material from a substrate surface by electrochemicaldissolution while concurrently polishing the substrate with reducedmechanical abrasion compared to conventional CMP processes. Theelectrochemical dissolution is performed by applying an electrical biasbetween a cathode and substrate surface to remove conductive materialsfrom a substrate surface into a surrounding electrolyte. Duringelectrochemical dissolution, the substrate typically is placed in motionrelative to a polishing pad to enhance the removal of material from thesurface of the substrate. In one embodiment of an ECMP system, theelectrical bias is applied by a ring of conductive contacts inelectrical communication with the substrate surface in a substratesupport device, such as a substrate carrier head. However, during ECMPprocesses, hydrogen bubbles formed at the cathode electrodes may come incontact with a surface of the substrate being polished. Hydrogen andother bubbles contacting the substrate electrically insulate that regionof the substrate from current carried by the electrolyte, therebylocally disrupting the polishing process. As the hydrogen bubbles arenot easily controlled and are often swept across the substrate'ssurface, the uniformity of the polishing process is difficult to controland results in poor polishing performance.

As a result, there is a need for an improved polishing apparatus.

SUMMARY OF THE INVENTION

Aspects of the invention generally provide a method and apparatus forpolishing a layer on a substrate using electrochemical depositiontechniques, electrochemical dissolution techniques, polishingtechniques, and/or combinations thereof. In one aspect, an apparatus isprovided for polishing a substrate that includes a conductive polishingpad and an electrode having a spacer disposed therebetween. The spacerhas a first surface facing the electrode that extends from a center ofthe spacer to an edge of the spacer. A portion of the first surfaceproximate the spacer's edge is closer to the conductive pad than aportion of the first surface proximate the spacer's center.

In another aspect, an apparatus for polishing a substrate includes aconductive polishing pad and an electrode having a permeable membranedisposed therebetween. The conductive polishing pad has a substantiallyplanar polishing surface. The membrane has a non-parallel orientationrelative the polishing surface of the conductive pad.

In another aspect, an apparatus for polishing a substrate includes abasin having sides and a bottom adapted to contain electrolyte during apolishing process and a plenum cap defining a plenum therebetween. Theplenum cap is disposed on the bottom of the basin and has a plurality ofapertures therethrough that are coupled to the plenum. A port formedthrough the bottom of the basin is coupled to the plenum.

In another aspect, an apparatus for polishing a substrate includes aconductive polishing pad and at least one polishing head adapted toplace a substrate retained in the polishing head in contact with theconductive polishing pad. The conductive polishing pad is disposed in atray and an electrode is disposed between the conductive polishing padand a bottom of the tray. A membrane is disposed between the conductivepolishing pad and the electrode. The membrane has an outer edge that isdisposed closer to the conductive pad than a center portion of themembrane.

In another aspect, an apparatus for polishing a substrate includes achemical mechanical polishing station, an electro-chemical polishingstation and a transfer device having at least one polishing head adaptedto selectively place a substrate retained in the polishing head incontact with the chemical mechanical polishing station or theelectro-chemical polishing station. The electro-chemical polishingstation may be coupled to an electrolyte delivery system. Theelectrolyte delivery system includes a plurality of baffles disposedtherein and at least one pump adapted to flow electrolyte between thetank and the electro-chemical polishing station.

In another aspect of the invention, a method for electro-chemicalpolishing a substrate is provided. In one embodiment, the methodincludes moving a substrate relative to a conductive polishing pad,flowing electrolyte between an electrode and the substrate, theelectrolyte providing a conductive path between the electrode and thesubstrate through the conductive polishing pad, and flowing electrolytethrough a membrane disposed between the electrode and the conductivepad, the membrane having an edge and a center portion, the edge disposedcloser to the conductive pad than the center portion.

BRIEF DESCRIPTION OF THE DRAWINGS

A more particular description of the invention, briefly summarizedabove, may be had by reference to the embodiments thereof that areillustrated in the appended drawings. It is to be noted, however, thatthe appended drawings illustrate only typical embodiments of thisinvention and, therefore, are not to be considered limiting of itsscope, for the invention may admit to other equally effectiveembodiments.

FIG. 1 is a sectional view of one embodiment of a processing cell of theinvention;

FIG. 2 is a sectional view of one embodiment of a settling tank takenalong section lines 2—2 of FIG. 1;

FIGS. 3A-F are various embodiments of conductive pads;

FIG. 4 is a partial sectional view of one embodiment of a conductiveelement of a conductive pad;

FIGS. 5A-C are bottom plans and partial sectional views of oneembodiment of a spacer;

FIG. 6 is an expanded sectional view of one embodiment of a tray;

FIG. 7 is a perspective view of one embodiment of an electrode;

FIG. 8 is a sectional view of one embodiment of a polishing system; and

FIG. 9 is a plan view of another embodiment of a polishing system.

To facilitate understanding, identical reference numerals have beenused, wherever possible, to designate identical elements that are commonto the figures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The words and phrases used herein should be given their ordinary andcustomary meaning in the art by one skilled in the art unless otherwisefurther defined herein. Chemical-mechanical polishing should be broadlyconstrued and includes, but is not limited to, abrading a substratesurface by chemical activity, mechanical activity, or a combination ofboth chemical and mechanical activity. Electropolishing should bebroadly construed and includes, but is not limited to, planarizing asubstrate by the application of electrochemical activity.Electrochemical mechanical polishing (ECMP) should be broadly construedand includes, but is not limited to, planarizing a substrate by theapplication of electrochemical activity, or a combination of bothelectrochemical and mechanical activity to remove material from asubstrate surface. Electrochemical mechanical plating process (ECMPP)should be broadly construed and includes, but is not limited to,electrochemically depositing material on a substrate and concurrentlyplanarizing the deposited material by the application of electrochemicalactivity, or a combination of both electrochemical and mechanicalactivity.

Anodic dissolution should be broadly construed and includes, but is notlimited to, the application of an anodic bias to a substrate directly orindirectly which results in the removal of conductive material from asubstrate surface and into a surrounding electrolyte solution. Apertureshould be broadly construed and includes, but is not limited to, aperforation, hole, opening, channel, or passage formed partially orcompletely through an object. Additionally, the term substantially asused to modifying the term planar is intended to describe a surface on amacroscopic or global level and not surface roughness.

FIG. 1 depicts a sectional view of one embodiment of a process cell 100in which at least one process comprising anodic dissolution, plating andpolishing processes may be practiced. The process cell 100 generallyincludes a basin assembly 104 and a polishing head 102. A substrate 108is retained in the polishing head 102 and disposed in the basin assembly104 during processing in a face-up (e.g., backside down) orientation. Anelectrolyte is flowed over the substrate's surface while the polishinghead 102 is placed in contact with the substrate 108. The substrate 108and a polishing surface disposed in the basin assembly 104 are movedrelative to each other to provide a polishing motion. The polishingmotion generally comprises at least one motion defined by an orbital,rotary, linear or curvilinear motion, or combinations thereof, amongother motions. The polishing motion may be achieved by moving either orboth of the polishing heads 102 and the basin assembly 104. Thepolishing head 102 may be stationary or driven to provide at least aportion of the relative motion between the basin assembly 104 and thesubstrate 108 held by the polishing head 102. In the embodiment depictedin FIG. 1, the polishing head 102 is coupled to a drive system 110. Thedrive system 110 moves the polishing head 102 with at least a rotary,orbital, sweep motion or combinations thereof.

The polishing head 102 generally retains the substrate 108 duringprocessing. In one embodiment, the polishing head 102 includes a housing114 enclosing a bladder 116. The bladder 116 may be deflated whencontacting the substrate to create a vacuum therebetween, thus securingthe substrate to the polishing head 102. The bladder 116 mayadditionally be inflated to press the substrate in contact with thepolishing surface of the basin assembly 104. A retaining ring 112 iscoupled to the housing 114 and circumscribes the substrate 108 toprevent the substrate from slipping out from the polishing head 102while processing. One polishing head that may be adapted to benefit fromthe invention is a TITAN HEAD™ carrier head available from AppliedMaterials, Inc., located in Santa Clara, Calif. Another example of apolishing head that may be adapted to benefit from the invention isdescribed in U.S. Pat. No. 6,159,079, issued Dec. 12, 2001, which ishereby incorporated herein by reference in its entirety.

The basin assembly 104 generally includes a tray 118 that houses anelectrode 120, a membrane 122, a spacer 124 and a conductive pad 126.The electrode 120 is generally disposed at the bottom of the tray 118.The spacer 124 is disposed above the electrode 120 and supports theconductive pad 126. The membrane 122 is disposed between the electrode120 and the spacer 124. The electrode 120, the membrane 122, the spacer124 and the conductive pad 126 are generally fastened or clamped to thetray 118. In one embodiment, at least the membrane 122, the spacer 124and the conductive pad 126 are fastened together using adhesives.

The basin assembly 104 is rotationally supported above a base 106 bybearings 134. A drive system 136 is coupled to the basin assembly 104and rotates the basin assembly 104 during processing. A catch basin 128is disposed on the base 106 and circumscribes the basin assembly 104 andcollects processing fluids, such as an electrolyte, that flow out of thebasin assembly 104 during processing.

An electrolyte delivery system 132 is generally coupled to the basinassembly 104. The electrolyte delivery system 132 flows electrolyte orother processing fluid into the basin assembly 104. During processing,the electrolyte generally provides an electrical path between theelectrode 120 and substrate 108 through the conductive pad 126.

The electrolyte used in processing the substrate 108 can polish metalssuch as copper, aluminum, tungsten, gold, silver or other materials thatcan be electro-chemically deposited onto or electrochemically removedfrom the substrate 108. Electrolyte solutions may include commerciallyavailable electrolytes. For example, in copper containing materialremoval, the electrolyte may include sulfuric acid based electrolytes orphosphoric acid based electrolytes and potassium phosphate (K₃PO₄), orcombinations thereof. The electrolyte may also contain derivatives ofsulfuric acid based electrolytes, such as copper sulfate, andderivatives of phosphoric acid based electrolytes, such as copperphosphate. Electrolytes having perchloric acid-acetic acid solutions andderivatives thereof may also be used. Additionally, the inventioncontemplates using electrolyte compositions conventionally used inelectroplating or electropolishing processes, including conventionallyused electroplating or electropolishing additives, such as brightenersamong others. In one aspect of the electrolyte solution, the electrolytemay be made of components (such as copper sulfate, for instance) havinga concentration between about 0.2 and about 1.2 Molar of the solution.

As one example, copper sulfate (CuSO₄) can be used as the electrolyte.One source for electrolyte solutions used for electrochemical processessuch as copper plating, copper anodic dissolution, or combinationsthereof is Shipley Leonel, a division of Rohm and Haas, headquartered inPhiladelphia, Pa., sold under the tradename ULTRAFILL 2000.

In one embodiment, the electrolyte is recirculated through the basinassembly 104. Electrolyte drains from the catch basin 128 through anoutlet 130 to a first pump 170. The first pump 170 is typically adiaphragm pump to minimize the effects of particulates or entrainedgases within the electrolyte on pumping. Other types of pumps mayalternatively be used.

The first pump 170 pumps the electrolyte through a filter 172 and into asettling tank 174. The filter 172 removes particulates, bubbles andother processing by-products from the electrolyte drained from the basinassembly 104. The filter 172 typically has a pore size in the range ofabout 15 to about 0.1 micron. In one embodiment, the filter 172 has a0.1 micron pore size, such as those available from Pall Company, locatedin East Hills, N.Y.

FIG. 2 depicts a sectional view of one embodiment of the settling tank174 taken along section lines 2—2 of FIG. 1. The settling tank includesa plurality of vertical baffles 202 disposed within the tank 174. Thebaffles 202 create an extended flowpath, as shown by flow arrows 204a-e, for the electrolyte pumped through the settling tank 174. Theextended path through the settling tank 174 increases the dwell time ofelectrolyte passing through the tank 174, thereby allowing moreentrained bubbles and debris to separate from the electrolyte flow as itpasses around the baffles 202. Gases, such as hydrogen, separated fromthe electrolyte generally are exhausted from the settling tank 174through a vent 178 (depicted in FIG. 1). Optionally, the volume abovethe electrolyte within the settling tank 174 may have a reduced,sub-atmospheric or vacuum pressure to enhance the removal of bubblesfrom the electrolyte within the settling tank 174.

Returning to FIG. 1, a second pump 176 pumps electrolyte from thesettling tank 174 through a rotary union 142 and into the basin assembly104. In one embodiment, the second pump 176 is a magnetic drivecentrifugal pump, although other types of pumps may alternatively beutilized. The path of the electrolyte through the basin assembly 104 isdescribed below in the detailed description of the components of thebasin assembly 104.

A power source 138 is coupled between the electrode 120 and theconductive pad 126. A slip ring 140 is provided at the center of thetray 118 to facilitate continuous electrical connection between theelectrode 120 and the conductive pad 126 as the basin assembly 104rotates.

While the following conductive pad 126 is described for anelectrochemical-mechanical polishing (ECMP) process, the inventioncontemplates using the conductive polishing media (pads) in otherfabrication processes involving electrochemical activity. Examples ofsuch processes using electrochemical activity include electrochemicaldeposition, which involves a conductive pad 126 being used to apply auniform bias to a substrate surface for depositing a conductive materialwithout the use of a conventional bias application apparatus, such asedge contacts, and electrochemical mechanical plating processes (ECMPP)that include a combination of electrochemical deposition and chemicalmechanical polishing.

The conductive pad 126 can be a pad, a web or a belt of material, whichis compatible with the fluid environment and the processingspecifications. In the embodiment depicted in FIG. 1, the conductive pad126 is circular in form and is adhered or otherwise retained in the tray118 on top of the electrode 120 opposite the polishing head 102. Theconductive pad 126 includes one or more conductive elements (not shownin FIG. 1) for contacting the surface of the substrate 108 duringprocessing. An optional backing material (not shown) may be disposedbetween the electrode 120 and the conductive pad 126 to tailor thecompliance and/or durometer of the conductive pad 126 during processing.Examples of a conductive pad that may be adapted to benefit from theinvention are disclosed in U.S. Provisional Patent Application No.60/286,107, filed Apr. 24, 2001 and No. 60/326,263, filed Oct. 1, 2001;U.S. Patent Provisional Application Serial No. 60/286,107, filed Apr.24, 2001; and U.S. patent application Ser. No. 10/033,732, filed Dec.27, 2001, all of which are incorporated herein by reference in theirentireties.

FIG. 3A depicts one embodiment of the conductive pad 126. The conductivepad 126 generally comprises a body 306 having a polishing surface 302adapted to contact the substrate while processing. The polishing surface302 has one or more pockets 304 formed therein to at least partiallyreceive a respective conductive element 314. The conductive elements 314generally have a contact surface 308 that extends above a plane definedby the polishing surface 302. The contact surface 308 is typicallycompliant to maximize electrical contact with the substrate. Duringpolishing, the substrate generally provides a bias force that urges thecontact surface 308 into a position co-planar with the polishing surface302.

The body 306 is generally permeable to the electrolyte by a plurality ofchannels or apertures 310 formed therein. The plurality of apertures 310allows electrolyte to flow through the body 306 and contact the surfaceof the substrate during processing. Apertures 310 formed in theconductive pad 126 may include perforations, channels, or holes in thebody 306 having a diameter between about 0.5 millimeters (mm) and about10 mm. While not shown in FIG. 3A, in one embodiment, the apertures 310may have a diameter about equal to the thickness of the conductive pad126, or an aspect ratio of about 1:5 between the thickness of theconductive pad 126 and the diameter of the apertures disposed therein.

The conductive pad 126 may have an aperture density between about 30percent and about 80 percent of the surface area of the conductive pad126 to provide for sufficient mass flow of electrolyte across thepolishing surface 302. In one embodiment, an aperture density of about50 percent provides sufficient electrolyte flow to facilitate uniformanodic dissolution from the substrate surface. Aperture density isbroadly described herein as the area or volume of conductive pad 126that the apertures 310 comprise of the surface or body of the conductivepad 126, i.e., the aggregate number and diameter or size of theapertures 310, when apertures are formed in the conductive pad 126.

The aperture size and density is selected to provide uniformdistribution of electrolyte, as well as current distribution, throughthe conductive pad 126 to a substrate surface. Generally, the aperturesize, aperture density, and organization of the apertures of theconductive pad 126 are configured and aligned relative to each other toprovide for sufficient mass flow of electrolyte through the body 306 tothe substrate surface.

The body 306 of the conductive pad 126 is generally made of a dielectricmaterial. Examples of materials suitable for use in the body 306 includeconventional polishing materials typically comprised of polymericmaterials, such as polyurethane, polycarbonate, fluoropolymers, TEFLON®,polyphenylene sulfide (PPS), or combinations thereof, and otherpolishing materials used in polishing substrate surfaces. Body materialsmay also contain fillers and/or be foamed. Exemplary conventionalmaterial includes those made from polyurethane and/or polyurethane mixedwith fillers, which are commercially available from Freudenberg withtheir FX9 pad. Other conventional polishing materials, such as a layerof compressible material, may also be utilized for the body 306.Compressible materials include, but are not limited to, soft materialssuch as compressed felt fibers leached with urethane or foam.

The pockets 304 generally are configured to retain the conductiveelements 314 while processing, and accordingly may vary in shape andorientation. In the embodiment depicted in FIG. 3A, the pockets 304 aregrooves of rectangular cross section and are disposed across thepolishing surface 302 coupling two points on the perimeter of theconductive pad 126. Alternatively, the pockets 304 (and conductiveelements 314 disposed therein) may be disposed at irregular intervals,be orientated radially, perpendicular and may additionally be linear,curved, concentric, involute curves or other orientation.

The conductive elements 314 generally have a bulk resistivity or a bulksurface resistivity of about 10 W-cm or less. In one embodiment, theconductive elements 314 have resistivity of about 1 W-cm or less.

Typically, the conductive elements 314 may include conductive polymers,polymer composites with conductive materials, conductive metals,conductive fillers or conductive doping materials, or combinationsthereof. Conductive polymers include polymeric materials that areintrinsically conductive, such as polyacetylene,polyethylenedioxythiophene (PEDT), which is commercially available underthe trade name BAYTRON™, polyaniline, polypyrrole, and combinationsthereof. Another example of a conductive polymer is silicon filled withnickel-coated carbon. Additionally, the conductive elements 314 mayinclude pure carbon fibers or coated carbon fibers, powder, flakes or becoated with any metal including noble metals.

Conductive elements 314 comprised of polymer composites with conductivematerials may include polymer-noble metal hybrid materials.Polymer-noble metal hybrid materials that may be used as conductiveelements 314 described herein are generally chemically inert with asurrounding electrolyte, such as those with noble metals that areresistant to oxidation and corrosion. An example of a polymer-noblemetal hybrid material is a platinum-polymer hybrid material. Embodimentsof the invention contemplate the use of polymer-noble metal hybridmaterials, which are chemically reactive with a surrounding electrolyte,when the polymer-noble metal hybrid material is insulated from asurrounding electrolyte by another material. Additionally, theconductive elements 314 may include a nonconductive polymer base coatedwith a conductive material, such as a noble metal.

Conductive elements 314 may include other conductive materials and/ormetals. Conductive metals that may be used as the conductive elements314 are those metals that are relatively inert to chemical reactionswith the surrounding electrolyte. One material that may be used isgraphite.

The conductive elements 314 may further include conductive fillers orconductive doping materials disposed in a binder material, such as theconductive polymers described above or a conventional polishingmaterial. Examples of conductive fillers include carbon powder, carbonfibers, carbon nanotubes, carbon nanofoam, carbon aerogels, andcombinations thereof. Carbon nanotubes are conductive hollow filamentsof carbon material having a diameter in the micron and nanometer sizerange. The conductive fillers or conductive doping materials aredisposed in the binding material in an amount sufficient to provide aconductive element 314 having a desired conductivity. The bindermaterial is typically a polymer. The conductive elements 314 mayalternatively be a conductive or dielectric material at least partiallycoated or covered with an at least partially conductive material such asthose described above. In one embodiment, the conductive elements 314are gold plated.

The conductive elements 314 generally have mechanical properties that donot degrade under sustained electric fields and are resistant todegradation in acidic or basic electrolytes. In one embodiment, theconductive elements 314 are compliant to maintain electrical contactbetween the entire contact surface 308 and the substrate duringprocessing. For example, the conductive elements 314 may have a hardnessof about 80 or less on the Shore D Hardness scale. In another aspect,conductive element 314 may have a hardness of about 50 or less on theShore D Hardness scale for polymeric materials.

In the embodiment depicted in FIG. 3A, the conductive elements 314 arecomprised of a conductive and compliant tubing fabricated from siliconfilled with nickel-coated carbon. The conductive elements 314 areembedded in the polishing surface 302 in a parallel, spaced-apartrelation at regular intervals. At least one aperture 310 is formedthrough the conductive pad 126 between each conductive element 314.

In another embodiment depicted in FIG. 3B, the conductive elements 314are comprised of a spring 316. The spring 316 is fabricated or coatedwith an at least partially conductive material as described above.

Returning to FIG. 3A, a connector 312 is utilized to couple theconductive elements 314 to the power source 138 through the slip ring140 (shown in FIG. 1) to electrically bias the conductive elements 314while processing. The connector 312 is generally a wire, tape or otherconductor compatible with process fluids or having a covering or coatingthat protects the connector 312 from the process fluids. The connector312 may be coupled to the conductive elements 314 by soldering,stacking, brazing, clamping, crimping, riveting, fastening, conductiveadhesive or by other methods or devices. Examples of materials that maybe utilized in the connector 312 include insulated copper, graphite,titanium, platinum, gold, and HASTELOY® among other materials. Coatingsdisposed around the connectors 312 may include polymers such asfluorocarbons, PVC and polyimide. In the embodiment depicted in FIG. 3A,one connector 312 is coupled to each of the conductive elements 314 atthe perimeter of the conductive pad 126. Alternatively, the connectors312 may be disposed through the body 306 of the conductive pad 126. Inyet another embodiment, the connector 312 may be coupled to a conductivegrid (not shown) disposed in the pockets and/or through the body 306that electrically couples the conductive elements 314.

FIG. 3C depicts another embodiment of a conductive pad 320. Theconductive pad 320 includes a conductive member 322 disposed in a pocket324 formed therein. The conductive member 322 is generally an at leastpartially conductive bar, cylinder or coil that includes a contactsurface 326 that extends above a plane defined by a polishing surface328 of the conductive pad 320. The contact surface 326 is generallyrounded to prevent damage to the substrate during processing.

A biasing member 330 is disposed between the conductive member 322 andthe conductive pad 320. The biasing member 330 generally provides a biasthat urges the conductive member 322 away from the conductive pad 320.The biasing member 330 is comprised of a resilient material or deviceand may be a compression spring, flat spring, coil spring, a foamedpolymer such as foamed polyurethane (e.g., PORON®), an elastomer, abladder or other member or device that urges the conductive member 322away from the conductive pad 320.

FIG. 3D depicts another embodiment of a conductive pad 340. A conductivemember 342 is disposed in a pocket 344 of the conductive pad 340. Theconductive member 342 generally comprises a plurality of pins or balls346. The balls 346 are at least partially comprised and/or coated withan at least partially conductive material as described above. Each ball346 includes a contact surface 348 that extends above a plane defined bythe polishing surface 354 of the conductive pad 340. The contact surface348 is generally rounded to prevent damage to the substrate duringprocessing.

The balls 346 are disposed through a bushing 350 disposed in the pocket344. The balls 346 may move through the bushing 350 so that the contactsurface 348 of the balls 346 may become substantially coplanar with thepolishing surface 354 when polishing.

A biasing member 352 is disposed between the conductive member 342 andthe conductive pad 340. The biasing member 352 generally provides a biasthat urges the conductive member 342 away from the conductive pad 340.The biasing member 352 is comprised of a resilient material or deviceand may be a compression spring, flat spring, coil spring, a foamedpolymer such as foamed polyurethane (e.g., PORON®), an elastomer, abladder or other member or device that urges the conductive member 342away from the pad 340. Typically, at least one of the biasing members352 or the bushing 350 comprises a conductive material or coating thatelectrically couples the balls 346.

FIG. 3E depicts another embodiment of a conductive pad 360. Theconductive pad 360 generally includes a conductive member 362 disposedin pockets 364 of the conductive pad 360. The conductive member 362generally includes a carrier 368 and a contact member 370. A biasingmember 366 similar to the biasing member 330 described above is disposedbetween the carrier 368 and the conductive pad 360 for urging thecontact member 370 to a position at least partially above a planedefined by a polishing surface 372 of the conductive pad 360.

The carrier 368 is typically formed from a conductive material such asgraphite or a metal or other material compatible with processchemistries as described above. Alternatively, other materials such assemiconductors or dielectric may be utilized. The carrier 368 isconfigured to remain in contact with the contact member 370 duringprocessing.

The contact member 370 is typically formed from a conductive materialsuch as graphite or a metal or other at least partially conductivematerial compatible with process chemistries as described above. Thecontact member 370 is typically a cylinder, coil, bar or ball althoughother shapes may be utilized. In the embodiment depicted in FIG. 3E, thecontact member 370 is a graphite rod seated on a graphite carrier 368.Alternatively, the contact member 370 may be a plurality of graphite orgold balls seated on and electrically coupled through a graphite carrier368.

FIG. 3F depicts another embodiment of a conductive pad 380. Theconductive pad 380 includes one or more at least partially conductiveelements 382 disposed on a polishing surface 384. The conductiveelements 382 generally comprise a plurality of fibers, strands and/orflexible fingers that contact the substrate while processing. Theconductive elements 382 are typically comprised of an at least partiallyconductive material as described above. In the embodiment depicted inFIG. 3F, the conductive elements 382 are a brush comprised ofelectrically conductive fibers, such as carbon fibers or otherconductive, compliant (i.e., flexible) element made from materialdescribed above.

The conductive elements 382 generally are disposed in a pocket 386formed in the polishing surface 384. The conductive elements 382 may beorientated between 0 and 90 degrees relative to the polishing surface384. In embodiments where the conductive elements 382 are orientatedparallel to the polishing surface 384, the conductive elements 382 maypartially be disposed on the polishing surface 384.

The pockets 386 have a lower mounting portion 388 and an upper,clearance portion 390. The mounting portion 388 is configured to retainthe conductive elements 382 by press fit, clamping, adhesives or byother methods. The clearance portion 390 is disposed where the pocket386 intersects the polishing surface 384. The clearance portion 390 isgenerally larger in cross section than the mounting portion 388 to allowthe conductive elements 382 to flex when contacting a substrate whilepolishing without being disposed between the substrate and the polishingsurface 384.

FIG. 4 depicts one embodiment of a brush 400 comprised of conductiveelements 402 (only four are shown for clarity). The brush 400 isgenerally orientated between 0 to 90 degrees relative to a polishingsurface 404 of a polishing pad 430 and can be inclined in any polarorientation relative a line normal to the polishing surface 404. Eachconductive element 402 generally comprises a ring or loop 406 having afirst end 408 and a second end 410 disposed in a pocket 412 formed inthe polishing surface 404. Each conductive element 402 is typicallyelectrically coupled to an adjoining conductive element to form aplurality of loops 406 extending above the polishing surface 404. Theends 408, 410 of the loops 406 may be secured in a conductive tray 414disposed in the pocket 412 to facilitate electrical connections andreplacement of the conductive elements 402. In the embodiment depictedin FIG. 4, each loop 406 may be fabricated from graphite, carbon fibers,made of twisted metal wires, for example, gold, stainless steel andplatinum, as well as polymer fibers coated with conductive metals, amongothers. In one embodiment, a polymer fiber may be plated with aconductive metal.

FIGS. 5A-C are bottom and sectional views of one embodiment of thespacer 124. The spacer 124 is typically fabricated from a materialresistant to process chemistry which will not detrimentally affectpolishing performance, for example a ceramic or polymer material such asfluoropolymers (for example, TEFLON®), polyethylene (PE),polyfluoroalkoxy resin (PFA), polyethersulfone (PES), high densitypolyethylene (HDPE), ultra high molecular weight polyethylene (UHMW),polyphenylene sulfide (PPS) and the like among others. The spacer 124generally supports the conductive pad 126 on a first side 502 within thetray 118. The first side 502 is orientated perpendicular to an axis ofrotation 508 of the spacer 126. A second side 504 is generally disposedon the electrode 120 or the tray 118. The second side 504 generallyincludes an angled surface 506 that is disposed at an angle 510 lessthan 90 degrees. Typically, the angle 510 is greater than about 75degrees, and in one embodiment, is about 88.5 degrees. The angularorientation of the angled surface 506 results in the spacer 124 beingthicker at a center 512 relative to an edge 514 of the spacer 124.

The second side 504 may additionally include a plurality of stiffeningribs 516. The stiffening ribs 516 are generally configured to provideparallelism between the first and second sides 502, 504 of the spacer124 so that the conductive pad 126 remains perpendicular to therotational axis 508 during processing. In embodiments where stiffeningribs are not utilized, at least one of the spacer 124, tray 118 or otherintermediate component is configured to maintain the perpendicularorientation between the axis 508 and conductive pad 126.

The stiffening ribs 516 generally add rigidity to the spacer 124 andprevent deflection of the first side 502 that disturbs the planarity ofthe conductive pad 126 supported thereon, resulting in poor polishingperformance. The stiffening ribs 516 may optionally include one or morenotches, channels, holes or other passages 526 that allow electrolyteflow between angled surfaces 506 disposed to adjacent sides of each rib516.

The spacer 124 is perforated or permeable to the electrolyte tofacilitate the flow of electrolyte to the substrate through theconductive pad 126. In one embodiment, a permeable ceramic spacer havinga thickness of about 0.5 inches and a pore size of about 100 microns wasdemonstrated to have acceptable polishing results. Different pore sizeand spacer thickness may be utilized to achieve a desired flow rate ofelectrolyte through the spacer 124 for a particular process.

In the embodiment depicted in FIGS. 5A-C, the spacer 124 includes aplurality of apertures 520 formed therethrough to allow electrolytethrough the spacer 124. The size and density of the apertures 520 areselected to provide uniform distribution of the electrolyte through thespacer 124 to the substrate 108. In one aspect, the spacer 124 includesapertures 520 having a diameter between about 0.5 mm and about 10millimeters. The apertures 520 may have a density between about 30percent and about 80 percent of the polishing media. Density of theapertures 520 of about 50 percent has been observed to provideelectrolyte flow with minimal detrimental effects to polishingprocesses. Generally, the apertures 520 of the spacer 124 and theconductive pad 126 may be aligned to provide for sufficient mass flow ofelectrolyte through the spacer 124 and conductive pad 126 to thesubstrate surface. In the embodiment depicted in FIGS. 5A-C, at leastone alignment hole 522 is formed through the spacer 124 and adapted toaccept a pin or fastener 524 disposed between the conductive pad 126 andspacer 124.

FIG. 5C depicts one embodiment of the membrane 122 disposed adjacent theangled surface 506. The membrane 122 is generally permeable, therebyallowing the electric field lines, electrolyte and other liquids anddiffused gases to pass therethrough. The membrane 122 generally preventsparticles, sludge and gas bubbles released from the electrode 120 frompassing through the electrolyte and contacting the substrate 120.Additionally, as the membrane 122 is maintained at the samenon-horizontal orientation as the angled surface 506, bubbles entrainedin the electrolyte (typically hydrogen gas generated at the electrode120 during processing) are substantially prevented from accumulating onthe membrane 122 as the inclination of the membrane 122 redirects thebubbles radially towards the edge 514 of the spacer 124 where they canescape between the pad 126 and the walls of the tray 118. This radialmovement of the hydrogen bubbles is additionally driven by thecentrifugal force generated by the rotating basin assembly 104. Thediverted bubbles thus pass around the pad 126 and therefore do not comein contact with the substrate 108 where diminished polishing performancecould result. Thus, the amount of hydrogen gas bubbles permeating themembrane 122 is substantially reduced resulting in improved polishing ofthe substrate.

The membrane 122 is typically fabricated from a porous ceramic orpolymer material that is compatible with process chemistries and doesnot increase the cell electrical resistance. The pore size is generallyselected to between about 0.1 and 10 micron. In one embodiment, themembrane 122 is fabricated from a non-woven polymer film such as TYVEK®.In the embodiment depicted in FIGS. 5A-C, the membrane 122 comprises aplurality of membrane elements 506 arranged in a polar array thatsubstantially cover at least the angled surfaces 506 of the spacer 124.Alternatively, the membrane 122 may comprise a single element.

FIG. 6 depicts a sectional view of one embodiment of a tray 118. Thetray 118 is generally comprised of a basin 610 and a plenum cap 612. Thebasin 610 and a plenum cap 612 are generally made of a plastic such asfluoropolymers, TEFLON®, PFA, PE, PES, or other materials that arecompatible with electroplating and electropolishing chemistries.

The plenum cap 612 generally has a cap plate 652 having a cap boss 654extending from a first side 656. At least one aperture 660 is formedthrough the cap plate 652 between the first side 656 and a second side658. The apertures 660 generally allow electrolyte to pass through theplenum cap 612. The apertures 660 are generally orientated at an acuteangle 662 relative to a centerline 664 of the plenum cap 612. In oneembodiment, eight (8) apertures 660 extend through the plenum cap 612 ina polar array.

The plenum cap 612 may be coupled to the basin 610 through a variety ofdevices and methods. For example, the plenum cap 612 may be adhered,press fit, staked, bonded or clamped to the basin 610. In the embodimentdepicted in FIG. 6, the cap plate 652 has a plurality of holes 678 (oneis shown) formed therethrough that respectively accept a fastener 676that threads into a hole 674 formed in the basin 610.

The cap boss 654 generally includes a passage 668 formed therethrough.The passage 668 allows leads 670 and 672 respectively coupled to theconductive pad 126 and electrode 120 through the slip ring 140 disposedbelow the tray 118. The lead 670 may be alternatively routed around theexterior of the basin 610 as shown by dashed line 670A.

The basin 610 generally defines a container or electrolyte cell in whicha conductive fluid such as the electrolyte can be confined. The basin610 may be stationary or be driven to provide at least a portion of arelative motion between the substrate 108 and the polishing head 102.

The basin 610 includes a sidewall 602 and a bottom 604. The sidewall 602is configured to have sufficient height that retains the electrode 120,the membrane 122, the spacer 124 and the conductive pad 126. The heightof the sidewalls 602 additionally provides adequate depth of electrolyteabove the conductive pad 126 so that the substrate retained in thepolishing head 102 is wetted by electrolyte during processing to ensurea conductive path between the substrate and electrode 120 through theconductive pad 126.

The bottom 604 of the basin 610 generally has an interior side 606 andan exterior side 608. The interior side 606 of the basin bottom 604generally supports the electrode 120. The interior side 606 additionallyincludes a stepped recess 614. The stepped recess 614 includes a capreceiving portion 616 that accepts at least a portion of the plenum cap612 and a second portion 618 typically disposed concentrically andradially inwards of the cap receiving portion 616. The plenum cap 612and the bottom 604 generally bound the second portion 618 to define aplenum that receives electrolyte flowing into the tray 118.

An inlet 620 is formed through the bottom 604 to fluidly couple thesecond portion 618 to the source of electrolyte used during processing.In one embodiment, electrolyte from the settling tank 174 is driven bythe pump 172 through the rotary union 142 and into second portion 618(i.e., plenum) by a conduit (not shown) coupled between the pump 172 andinlet 620. The apertures 660 of the plenum cap 612 may be configured torestrict the flow of electrolyte so that the electrolyte is uniformlydistributed about the second portion 618, resulting in uniform flow ofelectrolyte through the plenum cap 612 and to the substrate 108 (afterpassing through the other components disposed in the basin 610).

The second portion 618 of the stepped recess 614 has a boss 622extending from the bottom 604 towards the first side 606 of the basin610. The boss 622 generally supports the cap plate 652 of the plenum cap612 and circumscribes a center passage 624 disposed through the bottom608 of the basin 610. The center passage 624 accepts the cap boss 654 tolocate the plenum cap 612 and basin 610 when assembled while allowingrouting of the leads 670, 672.

Returning to FIG. 1, the electrode 120 is generally disposed between thetray 118 and the membrane 122. The electrode 120 is coupled to the powersource 138 by a lead (not shown) disposed through the tray 118 betweenthe slip ring 140 and the electrode 120. The electrode 120 generally isa counter-electrode to the substrate 108 and/or conductive pad 126contacting the substrate surface. The conductive pad 126 is at leastpartially conductive and may act as an electrode in combination with thesubstrate during electrochemical processes, such as an electrochemicalmechanical plating process (ECMPP), and electrochemical mechanicalpolishing (ECMP). The electrode 120 may be an anode or cathode dependingupon the positive bias (anode) or negative bias (cathode) appliedbetween the electrode 120 and conductive pad 126.

For example, when depositing material from an electrolyte onto thesubstrate surface, the electrode 120 acts as an anode and the substratesurface and/or conductive pad 126 acts as a cathode. When removingmaterial from a substrate surface, such as by dissolution from anapplied bias, the electrode 120 functions as a cathode and the substratesurface and/or conductive pad 126 acts as an anode for the dissolutionprocess.

The level of the electrolyte within the tray 118 is maintained at alevel that ensures that the electrode 120 and conductive pad 126 arewetted by the electrolyte to ensure current flow therebetween duringprocessing. The electrode 120 typically is comprised of the material tobe deposited or removed, such as copper, aluminum, gold, silver,tungsten and other materials which can be electrochemically deposited onthe substrate 108. For electrochemical removal processes, such as anodicdissolution, the electrode 120 may include a non-consumable electrode ofa material other than the deposited material, such as platinum forcopper dissolution. The non-consumable electrode is used inplanarization processes combining both electrochemical deposition andremoval. The electrode 120 is permeable to the electrolyte, and can be aplate-like member, a plate having multiple holes formed therethrough ora plurality of electrode pieces disposed in a permeable membrane orcontainer.

FIG. 7 depicts one embodiment of the electrode 120. The electrode 120generally includes an annular outer portion 702 and an inner web portion704. The inner web portion 704 is generally configured to have apercentage of open areas 710 that allows electrolyte to flow from theapertures 660 of the plenum cap 612 (see FIG. 6) substantiallyunobstructed. In one embodiment, the web portion 704 comprises aplurality of radially arranged spokes 706 that meet at a central hub708. The hub 708 generally provides a central location for the electrode120 to be coupled to the power source 138 by the lead 672, thusuniformly biasing the electrode 120 across its diameter. The web portion704 may alternatively be configured having other geometric or randompatterns.

An exemplary mode of operation of the processing cell 100 is describedas follows with reference to FIG. 1. In operation, the substrate 108 isretained in the polishing head 102 and moved over the conductive pad 126disposed in the basin 104. The polishing head 102 is lowered towards thetray 118 to place the conductive pad 126 in contact with the substrate108 or at least proximate thereto. Electrolyte is supplied to the basinassembly 104 and flows through the electrode 120 and conductive pad 126to a level that contacts the substrate 108. Substantially all of thehydrogen or other gas bubbles entrained in the electrolyte are separatedfrom the electrolyte, flowing outwards along the inclined membrane 122and away from the substrate as the electrolyte passes through themembrane 122. Electrolyte flows over the tray 118 and into the catchbasin 128 where it is directed to the electrolyte delivery system 132 ofrecycling.

A bias voltage is applied from the power source 138 between theconductive pad 126 and the electrode 120 through the rotary union 140.The bias between conductive pad 126 and the electrode 120 results in theremoval of conductive material, such as copper, disposed on the surfaceof the substrate 108, by an anodic dissolution method.

The substrate 108 and conductive pad 126 are moved relative to oneanother to uniformly polish the substrate surface. A contact force ofabout 6 psi or less is typically used to hold the substrate 108 againstthe conductive pad 126. A contact force of about 2 psi or less may beused when polishing substrates containing low dielectric constantmaterial.

In anodic dissolution, the bias is applied to the electrode 120,performing as a cathode, and the conductive pad 126 and the substrate108, performing as the anode. The application of the bias allows removalof deposited material from the substrate surface. The bias may includethe application of a voltage of about 15 volts or less to the substratesurface. A voltage between about 0.1 volts and about 10 volts may beused to dissolve copper-containing material from the substrate surfaceinto the electrolyte. Alternatively, the bias may be a current densitybetween about 0.1 milliamps/cm² and about 50 milliamps/cm², or betweenabout 0.1 amps to about 20 amps for a 200 mm substrate. It is believedthat biasing the substrate via the conductive pad 126 provides uniformdissolution of conductive materials, such as metals, into theelectrolyte from the substrate surface as compared to conventionalpolishing devices which bias the substrate through the substrate'sperimeter.

The bias applied to perform the anodic dissolution process may be variedin power and application, depending on the user requirements in removingmaterial from the substrate surface. For example, a time varying anodicpotential may be provided to the conductive pad 126. The bias may alsobe applied by electrical pulse modulation techniques. In one embodiment,a electrical pulse modification technique includes applying a constantcurrent density or voltage over the substrate for a first time period,then applying a constant reverse voltage over the substrate for a secondtime period, and repeating the first and second steps. For example, theelectrical pulse modification technique may use a varying potential frombetween about −0.1 volts and about −15 volts to between about 0.1 voltsand about 15 volts.

Conductive materials can be removed from at least a portion of thesubstrate surface at a rate of about 15,000 Å/min or less, such asbetween about 100 Å/min and about 15,000 Å/min. In one embodiment of theinvention where the copper material to be removed is less than 12,000 Åthick, the voltage may be applied to the conductive pad 126 to provide aremoval rate between about 100 Å/min and about 8,000 Å/min.

FIG. 8 depicts one embodiment of a polishing system 800 having a processcell 802 suitable for electrochemical deposition and/or chemicalmechanical polishing, such as electrochemical mechanical polishing(ECMP) or electrochemical mechanical plating processes (ECMPP) station.The process cell 802 generally includes a base 842 having a basinassembly 806 disposed thereon and a head assembly 810 supported over thebasin assembly 806 by a head assembly frame 852. The basin assembly 806is generally similar to the basin assembly 104 described above, and maybe coupled to or rotated above the base 842 on one or more bearings 808(one is shown).

The head assembly 810 includes a polishing head 812 that retains asubstrate 804 and can move to place the substrate 804 in contact with aconductive polishing pad 814 retained in the basin assembly 806 duringprocessing. The polishing head 812 is generally similar to the polishinghead 102 described above.

The head assembly 810 is generally mounted onto the head assembly frame852 that includes a mounting post 854 and a cantilever arm 856. Themounting post 854 is mounted to the base 842 of the polishing system800, and the cantilever arm 856 extends laterally from an upper portionof the mounting post 854. The mounting post 854 may provide rotationalmovement with respect to a vertical axis along the mounting post toallow the head assembly 810 to move laterally. The head assembly 810 isattached to a mounting plate 860 disposed at the distal end of thecantilever arm 856. The lower end of the cantilever arm 856 is connectedto a cantilever arm actuator 820, such as a pneumatic cylinder, mountedon the mounting post 854. The cantilever arm actuator 820 providespivotal movement of the cantilever arm 856 with respect to the jointbetween the cantilever arm 856 and the mounting post 854. When thecantilever arm actuator 820 is retracted, the cantilever arm 856 movesthe head assembly 810 away from the basin assembly 806 to provide thespacing required to remove or load the substrate from the basin assembly806 of the polishing system 800. When the cantilever arm actuator 820 isextended, the cantilever arm 856 moves the head assembly 810 andsubstrate 804 toward the basin assembly 806 to contact the conductivepolishing pad 814 retained in the basin assembly 806.

The head assembly 810 generally comprises the polishing head 812 and apolishing head actuator 858. The polishing head actuator 858 is coupledto the mounting plate 860, and includes a head shaft 862 extendingdownwardly through the mounting plate 860. The lower end of the headshaft 862 is connected to the polishing head 812 to allow verticalmovement of the polishing head 812.

The substrate actuator 858 additionally may be configured to providerotary motion to the polishing head 812. Relative motion between thesubstrate and the polishing head 812 during the anodic dissolutionprocess typically enhances the polishing results. The polishing head 812can also be rotated as the polishing head 812 is lowered to contact thesubstrate with the conductive polishing pad 814 disposed in the basinassembly 806 as well as when the polishing head 812 is in a raised orpartially raised position. In a raised or partially raised position, thehead 812 may be spun to remove electrolyte from the polishing head 812.

FIG. 9 depicts one embodiment of a polishing system 900 having at leastone process cell 902 suitable for electrochemical deposition and/orchemical mechanical polishing, such as electrochemical mechanicalpolishing (ECMP) station and chemical mechanical polishing station 904disposed on a base 906 and having substrate transfer mechanism 908 fortransferring substrates between the process cell 902 and polishingstation 904. The process cell 902 is generally similar to the processingcell 100 described above.

The transfer mechanism 908 generally includes at least one polishinghead 920 (three are shown) similar to the polishing head 102 describedabove. In the embodiment depicted in FIG. 9, the transfer mechanism 908includes a transfer device such as a carousel 922 that rotatablysupports a plurality of polishing heads 920 on an arm 926. One arm 926is removed to show a transfer station 928. One transfer station that maybe adapted to benefit from the invention is described in U.S. Pat. No.6,156,124, issued Dec. 5, 2000 to Tobin, which is hereby incorporatedherein by reference in its entirety.

Each polishing head 920 may be selectively positioned above one of theprocess cells 902 and polishing stations 904 to process the substrate. Asubstrate may be processed sequentially in any of the process cells 902and/or polishing stations 904 while remaining retained in a singlepolishing head 920. A drive system 924 is coupled to each of thepolishing heads 920 to facilitate at least a portion of the polishingmotion between the substrate and the process cell 902 or polishingstation 904 positioned therebelow. One transfer mechanism that may beadapted to benefit from the invention is described in U.S. Pat. No.5,738,574, issued Apr. 14, 1998 to Tolles et al., which is herebyincorporated herein by reference in its entirety.

The polishing station 904 generally includes a rotatable platen 910 thatsupports a polishing material 912. The polishing material 912 may be aconventional polishing pad, for example, a sheet of polyurethane and/orpolyurethane mixed with fillers, such as those generally commercially,or a polishing web of material comprising a plurality of abrasiveelements suspended in a polymer binder tensioned between rollersdisposed on either side of the platen 910. Typically, a polishingmedium, such as an abrasive slurry, de-ionized water or other liquid orpolishing compound is supplied between the polishing material 912 andthe substrate supported in the polishing head 920 to facilitate materialremoval from the substrate. One polishing system having a polishingstation that may be adapted to benefit from the invention is describedin U.S. Pat. No. 6,244,935, issued Jun. 12, 2001 to Birang et al., whichis hereby incorporated herein by reference in its entirety.

Therefore, the present invention substantially prevents gases fromreaching the substrate's surface during electrochemical processes. Thespacer and membrane, functioning individually or in concert, provide abarrier to gas passage. The basin assembly is configured to enhanceradial movement of gases away from the substrate. Moreover, thepolishing fluid delivery system is configured to remove entrained gases.As such, electrochemical processing of the substrate is enhanced.

While the foregoing is directed to various embodiments of the invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A polishing apparatus, comprising: a conductive polishing pad; anelectrode; and a spacer disposed between the electrode and theconductive polishing pad, the spacer having a first surface facing theelectrode extending from a center of the spacer to an edge of thespacer, wherein a portion of the first surface proximate the edge iscloser to the conductive pad than a portion of the first surfaceproximate the center of the spacer.
 2. The apparatus of claim 1, whereinthe first surface of the spacer comprises at least a portion of a cone,an ellipsoid, a sphere or a planar surface.
 3. The apparatus of claim 1,wherein at least a portion of the first surface of the spacer isorientated at an acute angle relative to a centerline of the conductivepolishing pad.
 4. The apparatus of claim 1, wherein the spacer ispermeable to electrolyte.
 5. The apparatus of claim 1, wherein thespacer is comprise a plurality of apertures formed therethrough.
 6. Theapparatus of claim 1, wherein the spacer is formed of a dielectricmaterial.
 7. The apparatus of claim 1, wherein the spacer is formed of apolymer.
 8. The apparatus of claim 1, wherein the spacer is formed of aceramic.
 9. The apparatus of claim 1, wherein the first surface of thespacer includes a plurality of ribs extending therefrom.
 10. Theapparatus of claim 1 further comprising at least one permeable membranedisposed adjacent the first surface.
 11. The apparatus of claim 1,wherein the membrane is adhered to the first surface.
 12. The apparatusof claim 1 further comprising a tray supporting the electrode, the trayhaving a port adapted to flow electrolyte to the conductive polishingpad.
 13. The apparatus of claim 12, wherein the tray further comprises:a basin having sides and a bottom adapted to retain the electrode; and aplenum cap disposed on the bottom of the basin and defining a plenumtherebetween that is in fluid communication with the port.
 14. Theapparatus of claim 13, wherein the plenum cap further comprises: a capplate having a plurality of apertures formed therethrough, the aperturesin fluid communication with the plenum.
 15. The apparatus of claim 13,wherein the plenum cap further comprises: a cap plate having a pluralityof apertures formed therethrough, the apertures in fluid communicationwith the plenum and orientated at an acute angle relative to a centeraxis of the plenum cap.
 16. A polishing apparatus, comprising: aconductive polishing pad having a substantially planar polishingsurface; an electrode; and a permeable membrane disposed between theelectrode and the conductive polishing pad, the membrane having anon-parallel orientation relative the polishing surface of theconductive pad.
 17. The apparatus of claim 16, wherein the membrane hasa form comprising at least a portion of a cone, an ellipsoid, a sphereor a planar surface.
 18. The apparatus of claim 16, wherein at least aportion of the membrane is orientated at an acute angle relative to acenterline of the conductive polishing pad.
 19. A polishing apparatus,comprising: a conductive polishing pad having a substantially planarpolishing surface; an electrode; a spacer disposed between the electrodeand the conductive polishing pad, the spacer having a first surfacefacing and substantially parallel to the polishing surface, and a secondsurface facing the electrode; and a permeable membrane disposed adjacentthe second side of the spacer, the membrane having a first portiondisposed closer to the conductive pad than a second portion.
 20. Theapparatus of claim 19 further comprising: a spacer disposed between themembrane and the conductive polishing pad, the spacer having a firstsurface facing and substantially parallel to the polishing surface, anda second surface following a contour of the membrane.
 21. The apparatusof claim 19 further comprising: a basin having sides and a bottomadapted to retain the electrode; a port formed through the bottom; and aplenum cap disposed on the bottom of the basin and having a plurality ofapertures therethrough, the basin and plenum cap defining a plenumtherebetween, the port and apertures in fluid communication with theplenum.
 22. A polishing apparatus, comprising: a conductive polishingpad having a polishing surface substantially perpendicular having acentral axis; an electrode disposed adjacent the tray bottom; and apermeable membrane disposed between the electrode and conductivepolishing pad in an orientation non-perpendicular to the central axis.23. Apparatus for polishing a substrate, comprising: a basin havingsides and a bottom adapted to contain electrolyte during a polishingprocess; a plenum cap disposed on the bottom of the basin and plenum capdefining a plenum therebetween; a plurality of apertures formed throughthe plenum cap and coupled to the plenum; and a port formed through thebottom of the basin and coupled to the plenum.
 24. The apparatus ofclaim 23, wherein the bottom comprises: a first recess formed thereinthat accepts at least a portion of the plenum cap; and a second recessformed in the bottom inwards of the first recess, the second recessforming the plenum.
 25. Apparatus for polishing a substrate, comprisinga basin having sides and a bottom adapted to contain electrolyte duringa polishing process; a plenum cap coupled to the bottom of the basin andhaving a plurality of apertures formed therethrough, the basin andplenum cap defining a plenum therebetween; a port formed through thebottom of the basin and coupled to the plenum; a plurality of aperturesformed through the plenum cap and coupled to the plenum; an electrodedisposed adjacent the plenum cap; a membrane disposed adjacent theelectrode, the membrane having a center section disposed closer to thebottom of the basin than an edge of a membrane; and a conductivepolishing pad disposed adjacent the membrane.
 26. A polishing apparatus,comprising a tray; a conductive polishing pad disposed in the tray; anelectrode disposed between the conductive polishing pad and a bottom ofthe tray; a membrane disposed between the conductive polishing pad andthe electrode, the membrane having an outer edge and a center portion,wherein the outer edge is disposed closer to the conductive pad than thecenter portion; and at least one polishing head adapted to place asubstrate retained in the polishing head in contact with the conductivepolishing pad.
 27. A polishing apparatus, comprising: a) a chemicalmechanical polishing station comprising: at least one platen; apolishing material disposed on the platen; a polishing fluid deliverysystem adapted to provide a polishing fluid to the polishing material;b) an electrochemical polishing station comprising: at least one traydisposed adjacent the platen; a conductive polishing pad retained by thetray; an electrode disposed between the conductive polishing pad and thetray; a membrane disposed between the conductive polishing pad and theelectrode, the membrane having an outer edge and a center portion,wherein the outer edge is disposed closer to the conductive pad than thecenter portion; and c) a transfer device comprising: at least onepolishing head adapted to selectively place a substrate retained in thepolishing head in contact with the conductive polishing pad or thepolishing material.
 28. The apparatus of claim 27 further comprising anelectrolyte delivery system coupled to the tray, the electrolytedelivery system comprising a tank having a plurality of baffles disposedtherein and at least one pump adapted to flow electrolyte between thetank and the tray.
 29. The apparatus of claim 28, wherein the tankfurther comprises an aperture adapted to allow removal and/or escape ofgas from said tank.
 30. A method for electrochemical polishing asubstrate, the method comprising: placing the substrate parallel to asurface of a conductive pad; moving the substrate relative to theconductive polishing pad; flowing electrolyte between an electrode andthe substrate, the electrolyte providing a conductive path between theelectrode and the substrate through the conductive polishing pad andthrough a membrane disposed between the electrode and the conductivepad, the membrane having an edge and a center portion, the edge disposedcloser to the conductive pad than the center portion.
 31. The method ofclaim 30, further comprising: flowing the electrolyte to the electrodethrough a plurality of apertures formed in a tray supporting theelectrode.
 32. The method of claim 31, wherein the apertures are coupledto a common plenum formed in the tray.
 33. The method of claim 30,wherein gas entrained in the electrolyte is moved radially outward alongthe surface of the spacer of the membrane.
 34. The method of claim 30further comprising: removing gas from the electrolyte prior tocontacting the electrode.
 35. The method of claim 34 wherein the step ofremoving gas further comprises flowing the electrolyte through a seriesof baffles disposed in a tank.
 36. The method of claim 34, furthercomprising venting gas the tank.
 37. The method of claim 34, furthercomprising reducing pressure of an atmosphere above the electrolyte inthe tank.
 38. The method of claim 34 further comprising filtering theelectrolyte prior to flowing electrolyte to the electrode.